ref: upgrade pytest-rerunfailures (#81116)

this should allow us to upgrade pytest finally

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Author: asottile-sentry

requirements-dev.txt

@@ -14,7 +14,7 @@ pytest-cov>=4.0.0
 pytest-django>=4.9.0
 pytest-fail-slow>=0.3.0
 pytest-json-report>=1.5.0
-pytest-rerunfailures>=14
+pytest-rerunfailures>=15
 pytest-sentry>=0.3.0
 pytest-xdist>=3
 responses>=0.23.1